Statement of Problem: Within Florida, dozens of foreign
non-native fishes have established self-sustaining populations. There is concern that these introduced
species could negatively affect native communities by predation, competition,
or by serving as vectors for disease. The African jewelfish (Hemichromis
letourneuxi) is known to be territorial, aggressive and predacious on
native species. Its recent
expansion across south Florida has caused concern, as it is effect on the
native community is unclear. Neither is it clear to how stop or slow the spread of this invasive
species. Methods to
control/eradicate non-native fishes are critically needed, yet little work is
being done on their development.

Specific Relevance to Major Unanswered Questions and Information Needs
Identified: At present, the only management
techniques available to control non-native fishes are physical removal (e.g.,
electroshocking), dewatering or ichthyocides. Unfortunately, all of these methods
negatively impact native fauna as well as the targeted non-native fishes and
require a great deal of effort (and therefore, funding). Herein, we propose development and
testing of a genetic technique (Trojan Y) to control non-native fishes. Currently, the concept of using Trojan Y
technology to control non-native species exists solely as a theoretical
construct. Our project is the first
to attempt application of this theory to the real world (in this case, the
Greater Everglades). If we are
successful in development of the technology, it could potentially be applied to
a wide variety of species, including other fishes (e.g., brown hoplo Hoplosternum littorale), invasive
applesnails (Pomaceaspp.), the
Australian red claw crayfish (Cheraxspp.) and the green mussel (Perna viridis).

Status:

Species selection: We began this project by testing two
candidate species: African
jewelfish and Mayan cichlid (Cichlasoma
urophthalmus). After developing techniques to breed both species in the
laboratory, we decided to halt work on Mayan cichlid and focus on African
jewelfish. Some reasons for this
include:

Short generation time of African jewelfish (significantly shorter
than Mayan cichlid).

Small
body size of African jewelfish allows us to house more fish in the lab.

F1 generation: In previous years we collected wild
African jewelfish from south Florida, bred them in the lab (to produce the F1
generation) and feminized all the young. This resulted in a population of F1 females with a genetic makeup of
either XX or XY (hereafter termed F1XX and F1XY).

F2 generation: We then bred ten F1
females to wild males, producing ten F2 broods. The broods from the F1XY females will
contain the F2YY males, while the broods from the F1XX females are not useful
to us. At this time, we cannot
discriminate the F1XY females from the F1XX females, as they all look the same
(phenotypically). We also cannot
visually identify which of the F2 broods contain YY males (if any).

Planned Products:

USGS Fact Sheet on the application
of Trojan Y technology for non-native fish control in the Greater Everglades

Then we go back to breeding . . . (this work will likely be completed
in future years)

Breeding

Depending on the
outcome of the wild-bred batches (3, above), we may need to do some work to
look at temperature-dependence of male:female ratios.

Breed F1XY females to F2YY
males, then feminize the brood. Use
genetic techniques developed in 4 (above) to differentiate F3YY females (keep)
from F3XY females (discard).

Future studies:

Gynogenesis experiment -- can we create gynogens? This will allow us to confirm the XY or
ZW sex-determination system as well as produce large numbers of YY males and YY
females. However, it is very
experimental and may require some time to complete. This step is NOT critical to the
project, but would be helpful.

Life history/Behaviour studies -- We would like to work
closely to observe and quantify the life history and behaviour of YY females,
comparing them to XX females. Some
of the questions we would like to answer include:

What
is the lifespan of YY females? Is
it longer or shorter than XX females?

What
is the fecundity and survival of broods from YY females?

What
is the likelihood of males choosing to mate with YY females versus XX females?

What
is the aggression level/social development of YY females? Can they pass as XX?

Population-level studies -- We would like to conduct
population-level studies here at our facility (either in ponds or mesocosm
facility). I am working closely
John Teem (Department of Agriculture and Consumer Serves, Tallahassee), who
developed the theory of applying Trojan Y technology to the eradication of a
population. I hope to continue
partnering with him, especially in this phase when we conduct some small-scale
population-level studies and compare our real-life results to his theoretical
outcomes.